Beryllium

Beryllium (Be) was first detected by the French chemist Louis Nicolas Vauquelin, who in 1798 reported that he had discovered a 'new earth' by dissolving the mineral beryl in an alkali. He named this new substance 'glucine', from the Greek word for sweet, because of the sweet taste of some of its compounds(!) (N.B. It is now known that beryllium is toxic, corrosive to tissue, and can cause a life-threatening allergic disease called berylliosis, so tasting beryllium compounds is no longer recommended.) The German chemist Friedrich Wöhler isolated elemental beryllium in 1828 by reacting potassium with beryllium chloride, and was the first to use the name 'beryllium'. Antoine Bussy independently isolated beryllium by the same method in the same year.

Beryllium is the first of the group 2, or alkaline earth, metals. It has a very small atomic radius, which results in very high ionisation energies. This in turn means that all of beryllium's compounds are covalent, unlike the other alkaline earth metals, which usually form ionic compounds.

The most important use of beryllium is in radiation windows for X-ray tubes. Beryllium is transparent to both X-rays and gamma rays, which makes it ideal for this application. Beryllium is also transparent to energetic particles, and so it is also used to build the beam pipe in particle accelerators. Due to its light weight, beryllium is used in high-speed aircraft, guided missiles and satellites. Between 1998 and 2000, the McLaren formula one team used beryllium-aluminium-alloy pistons in their engines, although this was subsequently banned.

Lithium

The discovery of lithium (Li) is credited to the Swedish chemist Johan August Arfwedson, who in 1817 detected the presence of an unknown element in the mineral petalite. He named the element 'lithium', from the Greek lithos meaning stone. Elemental lithium wasn't isolated until 1821, when the English chemist William Thomas Brande obtained it from the electrolysis of lithium oxide.

Lithium is the first of the alkali metals. It possesses a single valence electron that is easily lost to form a cation with a 1+ charge. This means that lithium is a good conductor of heat and electricity, and is a highly reactive element, although it is the least reactive of the alkali metals. Lithium is soft enough to be cut with a knife - when cut it has a silver colour that quickly tarnishes on exposure to air. This is due to a reaction with oxygen to form lithium oxide. Lithium is a solid at room temperature and has the highest melting and boiling points of the alkali metals. It is also the lightest metal in the periodic table and has the lowest density of all non-gaseous elements.

Lithium's low density means that it can float on water, however it also reacts with water to form hydrogen gas and lithium hydroxide. Lithium's reaction with water is less vigourous than that of the other alkali metals but is still fun to watch. Don't try this at home!

The largest use of lithium is in lithium-ion batteries (not to be confused with lithium batteries!). Lithium batteries use lithium metal as the anode and are non-rechargeable, while lithium-ion batteries use an intercalated lithium compound and can be recharged. Alloys of lithium with other metals such as magnesium and aluminium are used to make parts for aircraft. Lithium compounds are also commonly used in the treatment of bipolar disorder.

Helium

The first evidence of helium (He) was observed in 1868 by the French astronomer Jules Janssen, who observed an unknown yellow line in the spectrum of sunlight during a solar eclipse. Later in the same year, the English astronomer Norman Lockyer observed the same yellow line and concluded that it was caused by an element in the sun that was unknown on Earth. Lockyer and the English chemist Edward Frankland named this new element 'helium', from the Greek helios meaning sun. Helium wasn't isolated on Earth until 1895, when William Ramsay treated cleveite, a uranium-containing mineral, with acids. The Swedish chemists Per Teodor Cleve and Abraham Langlet isolated helium independently by the same method and in the same year. Helium is the only element to be discovered extraterrestrially before being found on Earth.

Helium is the first of the noble gases and is chemically inert under normal conditions, although unstable compounds such as HeNe, HgHe₁₀ and WHe₂ have been created using an electric glow discharge. Helium has the lowest melting and boiling points of all the elements, and except under extreme conditions, it is always observed as a monatomic gas.

One of helium's more amusing properties is the effect it has on the voice. Helium is less dense than air, and so sound waves travel faster in helium than in air. As the fundamental frequency of a gas-filled cavity is proportional to the speed of sound in the gas, inhaling helium causes the resonant frequencies of the vocal tract to increase in pitch, resulting in a higher voice. The opposite effect can be achieved by inhaling a gas that is more dense than air, for example sulphur hexafluoride. Be careful playing with gases though, as both helium and sulphur hexafluoride are asphyxiants.

The largest use of helium is as a cryogenic fluid for temperatures at or below 4.2 K. This mostly involves cooling the superconducting magnets in MRI scanners. Helium is also used as a lifting gas for balloons and airships, as it is lighter than air and, unlike hydrogen, is non-flammable.

Hydrogen

The discovery of hydrogen (H) is usually credited to Henry Cavendish, who, in 1766, named the gas produced in the reaction between a metal and an acid 'flammable air'. In 1781, Cavendish also observed that this gas burned in oxygen to form water. Antoine Lavoisier reproduced this finding in 1783, and named the gas 'hydrogen', from the Greek hydro meaning water and genes meaning creator.
 
Hydrogen is the most abundant chemical element in the universe, making up 75% of normal matter by mass and over 90% by number of atoms. Throughout the universe, it is usually found in its atomic or plasma forms, unlike on Earth, where it is always observed as a diatomic gas with formula H₂.

Hydrogen's ability to burn in air provided us with the famous 'squeaky pop' test, a favourite of Chemistry lessons everywhere. If hydrogen is produced in a reaction and a burning splint is placed near the gas, a loud 'pop!' will be heard. This sound is caused by the gas igniting.
 
Due to its low density, hydrogen was once widely used as a lifting gas for balloons and airships. This practice stopped after the 1937 Hindenburg disaster, in which the German airship LZ 129 Hindenburg caught fire and was destroyed during a landing attempt. 36 people were killed. Helium has now taken over as the lifting gas of choice, as, although it is heavier than hydrogen, it has the advantage of being non-flammable.
 
The most common modern uses of hydrogen are in the processing of fossil fuels and in the production of ammonia, an important ingredient of fertilisers. It is also used as a coolant for electrical generators at power stations, as it has the highest thermal conductivity of any gas. Liquid hydrogen is used as a rocket fuel in the space programme. Another use of hydrogen is as an energy carrier, as, unlike fossil fuels, it does not release CO₂ on burning. However, due to costs and difficulties with hydrogen storage, currently it isn't widely used.

A change of focus

I've decided to change the focus of my blog this year, mainly because Zintl ions, fascinating as they are, are a bit of a niche topic. There just aren't enough developments in this area of Chemistry for me to be able to write about it regularly, as shown by the pathetic number of posts for 2012. I will therefore go back to basics a bit and start writing about the elements. I will aim to write one post about each element on a fairly regular basis. The advantage of this is that I shouldn't run out of things to write about for a long time! Plus maybe I'll be able to provide some fascinating but little-known facts about the elements! Maybe... I'll be starting with hydrogen very soon, so watch this space!